NREL Studies Wind Farm Aerodynamics to Improve Siting

National Renewable Energy Laboratory, October 2013

NREL researchers are using advanced remote sensing instruments and high-performance computing to understand atmospheric turbulence and turbine wake behavior—a key to improving wind turbine design and siting within wind farms. As turbines and wind farms grow in size, they create bigger wakes and present more complex challenges to wind turbine and wind farm designers and operators.

Optimal Turbine Spacing In Fully Developed Wind Farm Boundary Layers

Johan Meyers and Charles Meneveau, Wiley Online Library, 2011

As wind farms become larger, the asymptotic limit of the ‘fully developed’, or ‘infinite’, wind farm has been receiving an increased interest. This limit is relevant for wind farms on flat terrain whose length exceeds the height of the atmospheric boundary layer by over an order of magnitude. Recent computational studies based on large eddy simulation have identified various mean velocity equilibrium layers and have led to parameterizations of the effective roughness height that allow the prediction of the wind velocity at hub height as a function of parameters such as wind turbine spacing and loading factors. In the current paper, we employ this as a tool in making predictions of optimal wind turbine spacing as a function...

Experimental Study of the Horizontally Averaged Flow Structure In A Model Wind Turbine Array Boundary Layer

Raúl Bayoán Cal, José Lebrón, Luciano Castillo, Hyung Suk Kang, and Charles Meneveau, American Institute of Physics, 27 January 2010

When wind turbines are deployed in large arrays, their ability to extract kinetic energy from the flow decreases due to complex interactions among them, the terrain topography and the atmospheric boundary layer. In order to improve the understanding of the vertical transport of momentum and kinetic energy across a boundary layer flow with wind turbines, a wind-tunnel experiment is performed. The boundary layer flow includes a 3 x 3 array of model wind turbines. Particle-image-velocity measurements in a volume surrounding a target wind turbine are used to compute mean velocity and turbulence properties averaged on horizontal planes. Results are compared with simple momentum theory and with expressions for...

Influence of the Vertical Wake Behind Wind Turbines Using A Coupled Navier-StokesVortex-Panel Methodology

Sven Schmitz, Jean-Jacques Chattot, University of California, Davis, 2005

The present paper introduces a parallelized coupled Navier-Stokes/Vortex-Panel solver (PCS) for incompressible high Reynolds number flow around horizontal axis wind turbines (HAWT). This coupling methodology reduces both artificial dissipation and computational cost. The coupled solver is applied to the NREL Phase VI rotor for fully attached flow. Results obtained for local blade loads are compared with experimental data and a vortex model based on a Lifting Line approach (VLM). It is indeed found that local blade loads obtained depend on at least ten revolutions of the vortex sheet in the wake.

Kinetic Energy Flux Measured by Lidar and Its Impact on Wind Turbines Power Performance 

Antoine Bégué*, Beatriz Canadillas, Thomas Neumann, Harald Mellinghoff, Deutsches Windenergie-Institut, Wilhelmshaven, Germany

In the scope of the RAVE (Research at Alpha Ventus) – LIDAR project, wind profile measurements from LIDAR (Leosphere - WindCube) are collected at the offshore platform FINO1. In the present work, some atmospheric parameters, such as the wind shear and the turbulence intensity, are investigated. The kinetic energy flux passing through the rotor area is also calculated by using LIDAR wind speed measurements at different heights. It is compared to the kinetic energy flux resulting only from the wind speed at hub height, as established in the IEC 61400-12-1 [1]. A new wind speed concept, the so-called “equivalent wind speed”, is defined as proposed by Risø DTU [2]. This wind speed takes into account the wind shear...

Review of CFD for Wind-Turbine Wake Aerodynamics

B. Sanderse, S.P. van der Pijl, B.Koren

This article reviews the state of the art of the numerical calculation of wind-turbine wake aerodynamics. Different CFD techniques for modeling the rotor and the wake are discussed. Regarding rotor modeling, recent advances in the generalized actuator approach and the direct model are discussed, as far as it attributes to the wake description. For the wake, the focus is on the different turbulence models that are employed to study wake effects on downstream turbines.

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